In neurosurgery operating microscopes are indispensable. Stereotaxic frames are invaluable tools as well because of the great precision with which they permit a neurosurgeon to place a probe with an accuracy on the order of 1mm. The goal of this project is to combine the functionality of the operating microscope with the accuracy of a stereotaxic frame by outfitting digital encoders on the stand which supports the microscope so as to monitor its exact position continuously with a computer. The precise knowledge of the microscope's position will permit the display of anatomic information such as a tumors outline in the focal plane of the microscope via a miniature video display. Preliminary simulations demonstrate that this is realizable with commercially available encoders. Our specific aim will be to very this with a prototype stand. This device will be tested by comparing its position as computed from the encoders with its actual position on precision milled blocks of known dimensions. It is believed that the commercial prospects of this project are very attractive given that any institution equipped to perform neurosurgical procedures will be a potential customer.